[ntp:questions] Re: PPS from TrueTime 468-DC GOES Time Receiver (with GPS antenna)

Hal Murray hmurray at suespammers.org
Thu Aug 24 21:11:28 UTC 2006


In article <1156450631.842127.105780 at 74g2000cwt.googlegroups.com>,
 "simonpg" <paul at thesimonet.org> writes:
>So I have this fine receiver and have been a member of pool.ntp.org for
>several years.  But I would like to take advantage of the PPS signal.
>The downside is that I have no idea where to start.  The upside is that
>I can solder and read a simple schematic diagram.  Any ideas?
>
>This is the first time in many years that I have used usenet.  I am
>trying the google interface.  My point is that I'm not totally
>confident that I will see any posts to this thread.  So please feel
>free to send e-mail; I'm sure the spammers will.

Have you found the web page for the driver?
  http://www.cis.udel.edu/~mills/ntp/html/drivers/driver5.html
(That may not be the latest one, it's just what google found for me.)

Lots of info here:
  http://www.leapsecond.com/museum/468-dc/theory.htm
That doesn't mention a PPS signal.  It says the signal is 468 MHz
so I wouldn't be surprised if a GPS antenna filtered that out.

The usual approach with a PPS signal is to connect it to
one of the RS-232 modem control signals.  (I forget which one, but
it should be easy to find.)  Most of the PPS signals are TTL levels
rather than RS-232.  If you want to get fancy you can wire up a
level converter (MAX-232) type chip but it will almost-for-sure
work with a direct connection.  You do have to get the inversion
right though - MAX-232 type chips are inverters.  Software can
normaly use either.

Once you get the signal into your box, try the ATOM (aka PPS) driver.

Is GEOS still working?  I found this note from June 2005 saying it
was going off the air:
  http://www.febo.com/pipermail/time-nuts/2005-June/001050.html


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